Electrical receptacle contacts of the type having opposing resilient contact beams designed for receiving contact pins are well known in the art. Typically, these electrical receptacle contacts may be gold plated or tin plated and therefore require the contact beams to provide various spring rates in order to produce consistent electrical performance. And, although different plating materials are employed which require contact beams of varying stiffness to impart different levels of force on contact pins, frequently, the overall dimensional shape of the contact must remain constant no matter what plating material is employed.
U.S. Pat. No. 5,067,916 discloses a method of making electrical receptacle contacts using various plating materials while providing sufficient spring forces for each respective plated contact and maintaining a constant overall dimensional shape of the receptacle. Thus an electrical receptacle contact of a given length plated with tin will produce the same electrical performance as a gold plated electrical receptacle contact of the same given length. Receptacle contacts such as the one disclosed in U.S. Pat. No. 5,067,916 utilize a common design having two symmetrically opposed contact arms. Rather than vary the length of the contact arm, the width and angles of the arms are adjusted to obtain appropriate spring forces while maintaining a constant overall dimensional shape.
As the width of the contact arm increases however, problems arise in forming the contact. In order to achieve a proper cylindrical structure, a stamped contact blank must undergo reverse bending in an area between each contact arm. As the contact arm width increases to impart the appropriate spring rate to the receptacle, the area between the contact arms decreases, thereby creating a relatively sharp edge between the contact arms during reverse bending rather than a desired rounded "W" shape. The sharp edge produced during reverse bending increases the likelihood of fracture of the receptacle during forming.
This reverse bending technique is necessary because alternative forming methods do not provide a uniform transition between the contact arms and the body of the contact by matching the forming radii of each. A uniform transition provided by reverse bending prevents thinning, flattening and fracturing which would adversely effect spring rate and spring forces.
Accordingly, what are needed are electrical receptacle contacts of constant overall dimensional shape which can provide a variety of spring forces accommodating different plating materials.